The PC PSP Emulator JPCSP has had a few revisions as of late, many improvements all round. In both visual quality and speed. Worth checking this latest build if you follow JPCSP.And also new users that what to try some PSP Emulation on their PC.

JPCSP v0.3 Revision 1246 Changelog:
Rev1246: First draft of GE viewport interpretation. [...]

Another jump in builds for JPCSP, the PC java based PSP emulator. So more tweaks and adjustments have been applied to further improve the emulators speed. If you want to try running a few of your PSP games on your PC then this is really the only application to use.
JPCSP v0.3 Revision 1191 Changelog:

Revision 1191: [...]

The JPCSP Team has updated their PC Java based PSP Emulator. So if you feel like trying a few PSP games on your PC, then this is the program for it. This new update – JPCSP v0.3 Revision 1183 features new bug fixes and added features.
PC PSP Emulator: JPCSP v0.3 Revision 1183 Changelog:

Revision 1182: VI2C.Q [...]

A new update from the the JPCSP team has been posted. JPCSP v0.3 Revision 1150 features new bugfixes and added features. JPCSP is a java PSP Emulator for PC.

JPCSP v0.3 Revision 1150 changelog:

r1150: Fixed small problem in MemoryReader
r1149: first attempt at sub intr support. GE callbacks and sub intr will now trigger on
r1148: [...]

The JPCSP team have posted another new update to their PC java PSP Emulator. The changelog below lists the changes made in JPCSP v0.3 Revision 1121.
JPCSP v0.3 Revision 1121 changelog:

r1116 Implemented sceIoRemove and sceIoChstat
r1118 First draft implementation for sceKernelRotateThreadReadyQueue
r1119 Fixed compilation problem due to non-UTF-8 character
r1120 Fix for “Tenchu: TOTA”
r1121 Fix for “Unbound Saga – [...]

The JPCSP Team have published another update for their Java PC PSP Emulator. More changes as listed below:
JPCSP v0.3 Revision 1114 Changelog:

r1114 Fixed again Spot light cutoff (thanks to Raziel for providing info).
r1113 Fixed decoding of Vertex Info: this should fix a lot of 3D rendering problems
r1112 Fixed IndexOutOfBoundsException introduced in r1111

Source: [...]

The last recent release a few days ago had a couple of bugs present, so to fix the known errors the JPCSP team have released a quick update fixing this. The changelog below shows what was fixed:
JPCSP v0.3 Revision 1107 Changelog:

r1107 – Avoid lot of “Using Compiler” log messages when exiting Jpcsp
[...]

The JPCSP team are back with another version of there Java PSP emulator for the PC. This version is over 50% fast than version 0.2 and includes many more bugs+fixes as listed below.
JPCSP v0.3 Revision 1105 Changelog.

A huge improvement in CPU/FPU/VFPU added and fixed a considerable instructions which make things better.
v0.3 is 50% faster than [...]

Another small update to the Java PSP Emulator. This latest build has updated findings in VfpuState, Plus a small fix in VCMOVT, VCMOVF and VHDP.
Changelog:
Uploaded REV 1098
Log last changes rev1096-1098
Quote:
r1098 Added more tests in VfpuTest. Updated findings in VfpuState: only small fix in VCMOVT & VCMOVF, VHDP confirmed.
r1097 Renamed SWB into VWB (to match prxtool) [...]

The JPCSP Team – creators of the PC Based Java PSP Emulator have released an update. This latest build has added basic GE capture support and more bug fixes.
JPCSP v0.2 Revision 1078 changelog:

Added basic GE capture support, tested on cube sample.
Until we record persistent GE state (texture on/off, etc) for best results
replay captures in the [...]

JPCSP.org have released another new build of their Java PSP Emulator. Revision 1064 bringsa few tweaks and bug fixes to the emulator.
Changelog:
r1064 added io ctl cmd 0×01010005 (umd file seek set, issue 88)
r1063 Fixed interpretation of Z for 2D Vertex, tested with 2DStudio.
r1062 sceIoPollAsync() should yield in all cases to allow the async IO to [...]

The team behind JPCSP (The Java PC PSP Emulator) have rolled out another update for this emulator. More tweaks and bug fixes. Here’s the changelog
Changelog:
* sceSasCore: fixed problem due to multi-threaded access (now synchronized methods)
* sceAudio: play the audio output larger than the AudioLine buffer size in a background thread (analog to sceSasCore). This should [...]

Keeping with improving the PC PSP emulator called JPCSP, the team has rolled out another update tweaking the emulator just that bit more. While not a huge changelog, its worth a mention for users following PC Java PSP emulation.
Changelog:
* updating syscalls/nids
Source: JPCSP Forums

The team over at JPCSP.org have released a new version of their popular PC Java PSP Emulator. This new release has the following changes added:

Updated the debugger:

Added address highlighting for jumps and branches.
Replaced the Look and Feel list selection with our own, now register highlighting on the selected line is readable.

RTC updated:

Fixed psp time fromMicros.
Improved [...]

The JPCSP project have released JPCSP v0.2 Revision 956. This is a Java PSP Emulator, that’s right not a PSP Emulator for the PSP – But a PC based PSP Emulator. No PSP required!
While in its early stages, it can emulator many PSP UMD games at a reasonable rate. Its no PSP, but the next [...]

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PSP Emulators, last updated: October 22nd 2009

Amiga PSP Emulator
Amstrad CPC PSP Emulator
Arcade Machine Emulators (CPS1 and 2, MAME and NEO GEO)
Atari 2600 PSP Emulator
Atari 7800 PSP Emulator
Atari 800/130XE/5200 PSP Emulators
Atari Lynx PSP Emulators
BBC Mirco Computer Emulator
Capcom Play System 1 (CPS1) PSP Emulator
Capcom Play System 2 (CPS2) [...]